Dune

Dune (dūŭn), n. [The same word as down: cf. D. duin. See Down a bank of sand.] A low hill of drifting sand usually formed on the coats, but often carried far inland by the prevailing winds. [Written also dun.]

Three great rivers, the Rhine, the Meuse, and the Scheldt, had deposited their slime for ages among the dunes or sand banks heaved up by the ocean around their mouths. Motley.